Homeostasis. what does it mean and how does it apply to the integumentary system

Homeostasis: the tendency toward a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes.
The integumentary system maintains homeostasis by protecting the body, regulating temperature, absorbing materials and synthesizing vitamins and minerals. 

Hope this helps!

They need to know because sometimes they have a symptom

Because without physical activity, the body has extra "energy" if you will, and so when it is time for bed you are not tired, so you end up staying up all night. also there is probably an effect on your internal clock, which messes with your melatonin production which goes hand in hand with your sleep cycle